Self-aligning thread roll for thread roll-snap gage



J. RATZKIN June 18, 1957 SELF-ALICNING ROLL FOR THREAD ROLL-SNAP GAGE Fflled June so, 1954 INVENTOR JACK RATZK|N $23M @pW ATTURXEYS United States Patent SELF-ALIGNING THREAD ROLL FOR THREAD ROLL-SNAP GAGE Jack Ratzkin, Greenbelt, Md., assignor to the United States of America as represented by the Secretary of the Navy Application June 30, 1954, Serial No. 440,565

(Granted under Title 35, U. S. Code (1952), see. 266) 1 Claim. (Cl. 33-199) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to a self-aligning thread roll for roll-snap thread gages and more particularly to a self-aligning thread roll for roll-snap thread gages having a structure which automatically compensates for thread lead error to allow accurate thread pitch diameter gaging.

Roll-snap thread gages of the character of this invention are designed generally for inspection of male thread errors and particularly for checking thread pitch diameters to allowable tolerances. The gaging rolls comprising such gages are provided with thread engaging ribs which are spaced apart to align the thread elements on the male thread test piece which are to be gaged for specific pitch diameter; however, these rolls do not embody in their structure compensating means for elimination of thread lead errors which prevent accurate pitch diameter measurement. Essentially, a single thread roll of the gage usually has merely one set of annular thread engaging ribs spaced apart from a second set of annular thread engaging ribs, thereby straddling a number of threads of the test piece and the lead error of each of the straddled threads becomes cumulative.

Another disadvantage of the known roll-snap thread gages is that it is difficult to prevent crossing of the threads or misalignment of the threads of the product as it is passed through the rolls of the gage, since contact between the roll ribs and the test product must be at re mote points along the longitudinal axis of the threaded piece in order to attempt to align the threads being measured. Obviously, a misalignment of the product threads when passing between the rolls of the gage gives an erroneous indication of the pitch diameter being gaged, since the annular ribs of the gage rolls would not measure the diameter of a single thread, but instead would gage a diameter defined by the V of one thread diametrically opposite the product of the V of an adjacent thread.

The deficiency of prior art thread rolls which allow lead errors to become additive to the gaged pitch diameter of a product is corrected by the present invention which is an improved gage roll having longitudinally spaced parallel annular ribs with resilient means posi- (iii 2,795,858 Patented June 18, 1957 along a direction parallel to the longitudinal axis of the gage roll to offset possible thread lead errors to allow precise gaging of thread pitch diameter.

A further object of the present invention is the provision of a gage roll for roll-snap thread gages having annular ribs thereon to straddle a large number of product threads and being laterally self-adjusting to serve as alignment ribs and lead error compensating ribs.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 shows a perspective view of a preferred embodiment of the invention mounted on eccentric pins supported in a U-shaped frame; and

Fig. 2 illustrates a sectional view taken substantially along the line 22 of Fig. 1.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in Fig. l a roll-snap thread gage 11 having a U-shaped frame 12. Go gage rolls 13, 14 and not go gage rolls 15, 16 are rotatably mounted on pins 17, 18 and 19, 20 respectively, and are positioned on the arms of the U-shaped frame 12 so as to form two pairs of rolls for measuring the maximum and minimum pitch diameter tolerances of an externally threaded product in a well-known manner.

Referring to Fig 2 there is shown a gage frame 12 having not go" or minimum tolerance thread pitch diameter rolls 15 and 16 mounted on the eccentric pins 19 and 20. The not go roll 15 is provided with annular thread engaging ribs 23 and 24 which are spaced apart to straddle a number of threads 21 of a product 22 and are each located on separate sleeve elements 25 and 26, respectively, of roll 15. A resilient member, such as compression spring 27, surrounds pin 19 and abuts the adjacent surfaces of sleeve elements 25 and 26. The resilient member 27 is provided to allow relative movement of the elements 25 and 26 of not go roll 15 in a direction substantially parallel to the longitudinal axis of pin 19. Similarly, not go" roll 16 is constructed of elements 28 and 29 separated by a resilient member such as spring 31 and is provided with spaced apart thread engaging ribs 32 and 33. it will be noted that the not go" rolls l5 and 16 have fewer ribs than go rolls 13 and 14 to obviate possible introduction of lead error to the check of the minimum pitch diameter of threads 21. Since a large number of thread engaging ribs 34 are present on rolls l3 and 14 to contact a like number of threads 21 of product 22, the problem of alignment of the threads 21 with ribs 34 is negligible. Also, the rolls 13 and 14 are spaced opposite each other on the arms of the U frame 12 to check the 3 accuracy of the maximum pitch diameter of the threads 21, and the lead error is relatively unimportant. However, not go rolls 15 and 16 are utilized to gage the minimum pitch diameter of the threads 21, and proper measurement is best obtained by checking only one or two threads to avoid introduction of lead error to the pitch diameter measurement. To compensate for accumulation of lead error the elements 25, 26 and 28, 29 are movable in a direction parallel to the axes of their respective supporting pins 19 and 20, and the ribs on elements 25 and 28 engage only one thread while the ribs on elements 26 and 29 align the ribs of elements 25 and 28 properly to prevent cross threading and at the same time adjust themselves to compensate for thread lead error by means of the axial movement allowed by resilient means 27 and 31.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

In a roll-snap thread gage having a U-shaped frame, minimum pitch diameter rolls rotatably mounted and diametrically opposed on said U-shaped frame comprising; a support pin fixed to one arm of said frame, a first twopart hollow cylindrical roll mounted for rotation on said support pin and having a truncated cone-shaped rib formed on each part of the cylindrical roll for engagement with a thread, a first compression coil spring surrounding said pin resiliently separating and axially spacing apart each part of said first cylindrical roll on said pin, a second support pin fixed to the other arm of said frame, a second two-part hollow cylindrical roll mounted for rotation on the second support pin and having two adjacent ribs forming a V for engaging a thread provided on each part of said second cylindrical roll, a second compression coil spring surrounding said second pin resiliently separating and axially spacing apart each part of said second cylindrical roll on said pin, the first and second minimum pitch diameter rolls being biased by said spring such that positive thread alignment of a threaded product to be gaged is obtained and thread lever error is discounted to allow accurate minimum pitch diameter measurement.

References Cited in the file of this patent U N lTED STATES PATENTS Aller et al. Jan. 16, [945 Gabbey June 5, 195! OTHER REFERENCES 

